1. (Field of the Invention)
The present invention relates to a rotation detecting device for use in various machines and equipments, for example, a rotation detecting device for detecting the rotation angle for the purpose of controlling the rotation of, for example, a small size motor, and a detector equipped bearing assembly having such rotation detecting device incorporated therein.
2. (Description of the Prior Art)
The rotation detecting device has been suggested in, for example, the Japanese Laid-open Patent Publication No. 2004-37133, hereinafter referred to as the Patent Document 1, which is of a design capable of incorporating in a small size machine or equipment and also capable of detecting the rotation angle with high precision and which utilizes a magnetic sensor unit made up of magnetic sensor arrays. This magnetic sensor unit includes, as shown in FIG. 11 of the accompanying drawings, a plurality of magnetic sensor arrays each made up of a plurality of magnetic sensor elements (MAGFETs), which are integrated on a sensor chip 42 together with a circuit unit 46 including, for example, a signal amplifying circuit, an analog-to-digital converting circuit and a digital signal processing circuit, with the sensor chip 42 being arranged in opposition to a magnet 44 that is mounted on a rotating member 41. In this case, the magnet 44 is of a kind having an anisotropy in a circumferential direction about the axis of rotation O and, on the sensor chip 42 referred to above, the magnetic sensor arrays 45 are arranged in a square pattern, with each array occupying one of four sides of the imaginary square shape.
With the rotation detecting device 43 so constructed as hereinabove described, respective outputs from the magnetic sensor arrays 45, each positioned along one side of the imaginary square shape, are read out by the signal amplifying circuit and the analog-to-digital converting circuit to detect a distribution of magnetic fields emanating from the magnet 44 and, based on a result of such detection, the rotation angle of the magnet 44 is calculated by a digital signal processing circuit.
Although different from the rotation detecting device 43 disclosed in the Patent Document 1, another rotation detecting device (such as, for example, a rotary encoder commercially available under the trade name of “LSI” manufactured by AMS Corp.) is also suggested, which makes use of magnetic sensor elements such as, for example, Hall elements so that the position of a magnet, fixed to a rotary body, and the movement of such magnet can be detected by calculating respective output signals from those magnetic sensor elements.